What is the best way to save a user's changes to a HTML app?

I am currently working on this website https://idle-chicken.glitch.me/chicken.html and I am trying to save the user's progress(the items they purchased, their eggs, cost, etc.) Right now the number of eggs as a cookie, but I was wondering if there is a way for me to save all of the changes both to the JavaScript and the HTML. I am fine using jQuery Javascript or AJAX (I think that is how you do it)?

This is what I am doing right now

function setCookie(cname, cvalue, exdays) {
  var d = new Date();
  d.setTime(d.getTime() + (exdays*24*60*60*1000));
  var expires = "expires="+ d.toUTCString();
  document.cookie = cname + "=" + cvalue + ";" + expires + ";path=/";
}

function getCookie(cname) {
  var name = cname + "=";
  var decodedCookie = decodeURIComponent(document.cookie);
  var ca = decodedCookie.split(';');
  for(var i = 0; i <ca.length; i++) {
    var c = ca[i];
    while (c.charAt(0) == ' ') {
      c = c.substring(1);
    }
    if (c.indexOf(name) == 0) {
      return c.substring(name.length, c.length);
    }
  }
  return "";
}

function checkCookie() {
  var cookie = getCookie("eggs");
  if (cookie != "") {
     eggs = cookie;
  } else {
      setCookie("eggs", eggs, 365);
  }
}

$(window).bind("beforeunload", function() {
  setCookie("eggs", eggs, 365);
  if (notThis) {
    return "Do you want to exit this page?";
  }
});

and then I do this for the HTML

<body onload="checkCookie()">